How to control particle's direction by animation node?
There is no way to alter the velocity or acceleration of particles of particle systems, the Blender python API doesn't allow it. However, if you want to control the general direction of particles, you can instance force fields and control their orientation and strength as suggested by  Jaroslav Jerryno. As an example, lets create a spiral spline in Animation Node and enable Curve Guide Force Field and Path Animation for it:



Or perhaps by animating a wind force field: